The present invention relates to a pump assembly design and to a method of making a pump assembly. More particularly, the present invention relates to a pump assembly design having increased efficiency, life, and dependability, as well as increased strength, rigidity, compatibility, and insulative characteristics over current pump assembly designs.
Pump assemblies have application in a variety of areas. Some of these assemblies are driven by motors that require a seal between the motor and a fluid being pumped to prevent the fluid from contacting the motor. Often, the seal is mounted on a shaft of the assembly that is driven by the motor. Over time, this seal tends to wear and, if not periodically checked and replaced, will allow fluid to contact the motor and damage it.
Some pump assembly designs utilize magnetic coupling between drive and driven motor members. Bumping or jarring of certain of these pump assembly designs can cause the drive and driven members to uncouple. When uncoupled, the motor of the assembly continues to operate but no pumping occurs. Pumping is reinitiated if the motor is turned off and restarted.
For pump assemblies to work efficiently and last, the drive components should be aligned. Also, misalignment of pump assembly drive components causes friction which increases wear and stresses of the components of the assembly.
Another pump assembly design consideration is dissipation of heat away from the assembly that is generated by the assembly electronics as well as the fluid being pumped. Excessive heat can stress components of these assemblies, such as electronics and bearings in which pump shafts are journaled.
A further consideration with certain pump assembly designs is compatibility with the fluid or fluids pumped. The materials from which these pumps are formed should be compatible or inert with fluids being pumped so these fluids do not become contaminated. Use of pump assemblies in the medical field, for such applications as kidney dialysis, is an example of where such compatibility or inertness is important.
In addition to forming an assembly from compatible or inert materials, it is also desirable to form pump assemblies from materials that are wear resistant and strong. This helps both protect the assemblies from damage by surrounding objects, as well as to increase the life and dependability of such assemblies.
The present invention is designed and directed to solving these above-described problems and meeting these above-described needs. An embodiment of the present invention includes a frame, a stator coupled to the frame, a rotor drivingly associated with the stator and configured to include a bore, and a housing configured to define a cavity in which the rotor is disposed, the cavity having a closed end and an open end. The embodiment also includes a first bearing secured in the closed end of the housing, a pump disposed adjacent to and driven by the rotor and stator, and a shaft coupled to the pump, disposed within and extending through the bore of the rotor, and journaled in the first bearing.
This embodiment of the present invention may also include a second bearing secured in the pump in which the shaft is journaled. In addition, the housing may be configured to include a flange adjacent the open end to which the pump is attached.
This embodiment of the present invention may further include an alignment spacer adjacent the open end of the housing and the pump that reduces lateral shifting of the pump relative to the housing. The alignment spacer may also be adjacent the open end of the housing and the pump to help facilitate alignment of a center of a bore through the first bearing with a center of a bore of the second bearing. The alignment spacer may be attached to the second bearing so that an inside periphery of the alignment spacer is in contact with an outside periphery of the second bearing and an outside periphery of the alignment spacer is in contact with an inside periphery of the open end of the housing. A seal may be disposed between the alignment spacer and a body of the pump. This seal may be positioned so as to be adjacent the pump, the inside periphery of the open end of the housing, and the outside periphery of the alignment spacer. In one or more embodiments, this seal may be an O-ring seal.
The alignment spacer may be configured to include a plurality of apertures in fluid communication with the pump and the cavity of the housing to thereby define a fluid flowpath including the pump, the alignment spacer, and the cavity of the housing. The first and second bearings may be configured to each include a channel. The channel in the first bearing may be in fluid communication with the cavity and the channel in the second bearing may be in fluid communication with the pump and the cavity of the housing. In this embodiment including the channels, a fluid flowpath may be defined from the pump, through the channel in the second bearing, through the cavity, the channel in the first bearing, the bore in the rotor, through the alignment spacer, and back to the pump.
The pump may include an inlet, an outlet, a gear, and a shaft. In this embodiment, a channel is formed in the first bearing. Also, in this embodiment, the gear and shaft are each configured to include a longitudinally extending bore therethrough. These bores are substantially aligned so that a fluid flowpath is defined through the bore in the gear and the bore in the shaft, to the channel in the first bearing, and to the cavity and the bore of the rotor. In this embodiment, the first bearing may be configured to include a recessed counterbore and an end of a body of the rotor may be configured to include a nose disposed adjacent the recessed counterbore to define a clearance between the nose and the recessed counterbore of the first bearing through which fluid in the fluid flowpath flows.
In embodiments of the invention including bearings, grooves may be formed in the outside peripheries of these bearings. Fluid pumped by the assembly flows or circulates through these grooves to help cool the bearings.
Allowing fluid pumped by the assembly to circulate in the manner described above lubricates the assembly. In addition, allowing such fluid flow provides for dissipation of heat generated during operation.
In embodiments of the present invention that include a shaft and one or more bearings, the shaft is journaled in the bearings and the rotor includes a body configured to define a bore in which the shaft is disposed. The shaft and bore may be configured so that the rotor is substantially restricted from movement about a longitudinal axis of the shaft and substantially unrestricted from movement in a direction along the longitudinal axis of the shaft. This allows the rotor to self-center within the stator so as to maximize energy transfer between the stator and rotor. The longitudinal bore extending through the body may be configured to include a key extending along a longitudinal length of the body that is received within a longitudinal slot formed in the shaft so that the key engages the slot to allow the rotor to move as described above. The body of the rotor may also be configured to provide a thrust surface for contact with one or more of the bearings.
The above-described components of the pump assembly constructed in accordance with the present invention are made from a material that is compatible or inert with the fluid being pumped. This helps reduce contamination of fluids pumped by the assembly and attack of the pump structure as well.
The rotor may be formed to include the above-described body and, in addition, a tube adjacent the body, a magnet adjacent the tube, and a shell adjacent the magnet so that the magnet is between the shell and tube. In one embodiment of the rotor, the body is made of polyphenylene sulfide polymer, the tube is made of steel, the magnet includes neodymium, iron, and boron, and the shell is stainless steel. The body may be made from other similar polymers as well.
In one or more embodiments of the pump assembly constructed in accordance with the present invention, the alignment spacer is made of plastic. Material reinforcements and lubricants are added to increase the strength and wear resistance of the alignment spacer. The above-described bearings may also be made of plastic. Material reinforcements and lubricants may be added to these bearings as well.
The housing may be made of a plastics material, and, in one embodiment, is a liquid crystal polymer. Use of a plastics material for the housing, in addition to providing compatibility, also helps provide heat insulation to electronic components used to control the operation of the pump assembly.
Another embodiment of a pump assembly constructed in accordance with the present invention, includes a frame, a stator coupled to the frame, a rotor associated with the stator, and a housing configured to define a cavity having an open end. This embodiment also includes a pump, driven by the rotor and stator, that includes a body secured to the housing, and an alignment spacer, adjacent the open end of the housing and the body of the pump, that reduces lateral shifting of the pump relative to the housing.
The open end of the housing may include an inside periphery and the alignment spacer may include an outside periphery in contact with the inside periphery of the housing. This embodiment may also include a seal adjacent the outside periphery of the alignment spacer, the inside periphery of the open end, and the body of the pump. This seal may be an O-ring seal.
This embodiment may further include the above-described first and second bearings, shaft, and fluid flowpaths. In addition, the alignment spacer may be positioned on the second bearing, as described above, and may also help facilitate substantial alignment of a center of the first bearing with a center of the second bearing.
The pump of this embodiment may include a drive member disposed within the pump and drivingly associated with a driven member also disposed within the pump. The shaft may be attached to the drive member. In one embodiment, the drive member may be a drive gear and the driven member may be a driven gear. The drive gear may include first and second faces and the driven gear may include third and fourth faces. In these embodiments, an insert may be positioned adjacent both the first and third faces and the second and fourth faces of the gears to reduce wear. These inserts also increase the dry run capability of the assembly. These inserts may be made from graphite and carbon.
This embodiment of the pump assembly constructed in accordance with the present invention may also be made from materials described above in connection with the first embodiment.
As discussed above, the present invention also relates to a method of making a pump assembly that includes a housing, a first bearing, a second bearing having an outside periphery, a body, and an alignment spacer having an inside periphery and an outside periphery. The method includes the steps of forming the housing to include a cavity having a closed end and an open end with an inside periphery. This method also includes the steps of securing the first bearing in the closed end of the housing, securing the second bearing in the body, attaching the alignment spacer to the second bearing so that the inside periphery of the alignment spacer is in contact with the outside periphery of the second bearing, and positioning the body adjacent the housing so that the inside periphery of the alignment spacer is in contact with the inside periphery of the open end, thereby substantially aligning a center of an opening through the first bearing with a center of an opening through the second bearing. The method in accordance with the present invention may also include forming the housing by forcing a plastics material through a mold so that the resulting structure is substantially free from knit lines normally caused by different plastic material flow fronts meeting one another. This helps increase the structural integrity of the housing. In one embodiment, the plastics material is a liquid crystal polymer which further helps increase the structural integrity of the rotor housing due to the relatively long molecular structure of such material.
The method may also include the step of ultrasonically welding the first bearing in the closed end of the housing and ultrasonically welding the second bearing in the body. The method may further include the steps of forming the housing to include a flange adjacent the open end and attaching the body of the pump to the flange.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.